13x^2+12x-81=0

Solution for 13x^2+12x-81=0 equation:

13x^2+12x-81=0

a = 13; b = 12; c = -81;
Δ = b2-4ac
Δ = 122-4·13·(-81)
Δ = 4356
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4356}=66$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-66}{2*13}=\frac{-78}{26}
=-3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+66}{2*13}=\frac{54}{26}
=2+1/13
$